Torpedoes can't catch up with their target.

[blin25]

The speed of heavy torpedoes is 67 m / s, the usual speed of any ship in the game is more than 100 m / s, so if the target moves the torpedoes with difficulty or never will get into it.

[Shehriazad]

Heavy torps are to be used Vs stations and carriers.

I've never had trouble....but I'd prefer heavy swarm missiles....faster, more damage if all missiles hit...and sexy fireworks.



EDIT:
Bonus pic of swarm goodness
https://i.redd.it/l174h2c1plf21.jpg


{Images posted directly to the forums should not be greater than 640x480 or 100kb, oversize image now linked - Terre}

[ZombiePotatoSalad]

They're meant to be used against stations. But if you must fire them at ships, try to hit them on the beam.
Or create a mod where they go faster. Possibly by coloring them red.

[Imperial Good]

Fire them from a modified Gorgon with exceptional forward thrust and chassis mod. The Gorgon should fly around 800m/s so firing a Heavy Torpedo from it at that speed will cause the Heavy Torpedo to start at 867 m/s and very slowly decelerate down. Needless to say L and XL ships will almost certainly be hit. Of course make sure the first heavy torpedo is to the engines since that renders their speed 0m/s so one cannot miss.